Cytokines for expansion and cell culture of mouse hematopoietic stem cells. Hematopoietic stem cells are self renewing pluripotent cells often characterized by the expression of CD34. Studies have shown that decreased expression of CD34 tends to correlate with decreased self renewal properties and pluripotent potential. Culturing CD34+ cells in a cytokine mixture of TPO, SCF, and FLT-3 Ligand for short time periods allows CD34+ cells to proliferate without decreasing CD34 expression, thus retaining their stem cell properties. The combination of these cytokines allows for the ex vivo expansion of the most immature hematopoietic stem cells in cord blood or bone marrow preparations, but can be supplemented with other cytokines to promote specific lineages. For example, GM-CSF and/or G-CSF can be added to promote monocytes and granulocytes while EPO can be added to promote erthroid cells. IL-6 and/or IL-3 can be used in conjuction with SCF and FLT-3 Ligand to promote expansion of more mature hematopoietic CD34+ progenitor cells.